Mountain Lion upgrades can take as little as 13 minutes and as long as almost an hour, a New York City Apple reseller said today.

Tekserve, which bills itself as "New York's largest independent Apple store," timed the Mountain Lion upgrades it installed on various Mac desktops and notebooks, averaged the scores for each model, and posted the results on its blog Wednesday.

"Unsurprisingly, the new [Retina] MacBook Pro was far and away the fastest to update, with the new MacBook Air models close behind," said Tekserve, which is located on West 23rd Street in Manhattan. "Their speed can be attributed to having solid state drives [SSD], which can access data much faster than a standard magnetic hard drive."

The Retina MacBook Pro, the 15-in. notebook with a higher resolution screen that Apple unveiled last month, completed the Mountain Lion upgrade in just 13 minutes, while the 11-in. and 13-in. MacBook Airs needed 17 minutes.

As Tekserve noted, those models rely on SSDs of various sizes to store data, applications and the operating system.

Machines with traditional platter-based drives, including the newest 13-in. and 15-in. MacBook Pros, and the two iMac models, required much more time to process the upgrade, ranging from 40 minutes for the 21.5-in. iMac to 57 minutes for the non-Retina 15-in. MacBook Pro.

Reviewers reported different upgrade times. Michael deAgonia, who examined Mountain Lion for Computerworld, said an upgrade to a SSD-equipped 15-in. MacBook Pro took approximately 35 minutes. Dan Frakes of Macworld -- like Computerworld, a site owned by IDG -- said his stopwatch recorded 15 to 25 minutes, depending on the Mac.

TUAW.com, or The Unofficial Apple Weblog, reported even-longer times of 30 to 50 minutes.

The Mountain Lion upgrade is a hands-off affair once the user has downloaded the 4GB installer from the Mac App Store, allowing Mac owners to step away from the machine and come back when the new OS is installed.

As in such cases, mileage may vary: Tekserve, for example, was upgrading new systems that lacked the digital detritus that accumulates on well-used Macs.